Synthesis and characteristics of non-stoichiometric nanocrystalline cerium oxide-based catalysts

Nanocrystalline materials are associated with high surface area and reactivity. Gas condensation techniques have been developed to synthesize such systems with a unique control of stoichiometry and dispersion. The high concentrations of oxygen vacancies and surface adsorbed species in nanocrystalline CeO_2-x were found to greatly enhance catalytic activity in SO₂ reduction and CO oxidation. By having an ultrahigh dispersion of Cu on nanocrystalline CeO_2-x, we have further demonstrated the possibility of tailoring intimate synergistic effects between different components in a nanocomposite material. The resulting supported base metal system has an unusually high thermal stability and could selectively catalyze SO₂ reduction and CO oxidation at significantly lower temperatures (420°C and 80°C, respectively). The high redox activity of the nanocrystalline CeO_2-x-based system is tied to the microstructure, surface chemistry, and electrical conductivity of this advanced catalyst.